I'll hazard a guess and say that you'll get a proper style cut at the 460 baht place, versus a hack job for 120 baht.
I used cheap places for a while and got dodgy haircuts but thankfully I found a nice place on Silom that gave me a nice new style for only 350 baht.
I even got a few compliments about it from my friends, that never happened after I went to the el cheapo places.
It's near the gay area, not that there's anything wrong with that.